2, Bangor University, Bangor, , United Kingdom
Crystalline secondary phases are often present in vitrified nuclear waste.
In this work interfaces are simulated between (Na2O)x(SiO2)1-x glasses (for x=0.0, 0.1 and 0.2) and TiO2 crystals using molecular dynamics and empirical potentials.
These calculations were used to investigate features and properties of such interfaces.
They showed that partially ordered layers had been induced in the glass close to the interfaces, with successive O-rich, Si-rich and Na-rich planes being noted.
The first silicate layer in contact with the crystal tended to be highly-structured, with Si ions occupying well-defined positions that depend on interface orientation, and showing 2-dimensional ordering depending on glass composition.
Results are presented suggesting that the structural flexibility of the glass network allows it to conform to the crystal, thereby providing charge compensation and avoiding large relaxation of the crystal structure close to the interfaces.
Such interfacial properties could be crucial to improving phenomenological models of glass-crystal composite wasteform properties.